As is known, the extremely widespread use of relays in many fields of electrical technology, telecommunications, electronics and, in particular, of automation is due to the versatility of the numerous types provided. In particular, the trend of manufacturing of electronic devices, which currently use the miniaturized relays, is to reduce their dimensions and make them as compact as possible.
The manufacturing of electronic devices aims most of all reduce the size of the relays, as well as to reducing the gauge of the electronic boards on which the relays are mounted.
In view of the above, relay manufacturers are therefore induced to manufacture relays that have smaller dimensions, especially in terms of height, and are increasingly sensitive, i.e. have a lower power consumption so as to reduce the dimensions of the power supply transformers.
A magnetic circuit of the current miniaturized relays has an electromagnet which is excited by an electric current which flows through its coil so as to attract a movable keeper or armature against a pole face or extension thereof.
The movement of the keeper is conveniently used to provide the required switching of the contacts.
The return of the movable keeper to the idle position, after the excitation current has ceased, is provided by means of a spring and generally by means of elastic contact-holder laminas of the relays.
The number, the arrangement of the contacts and the sequence of the movements naturally vary according to the purposes to which the relay is assigned.
Current power relays, depending on their structure, have their pole extensions arranged externally to the coil and/or shaped so as to generate magnetic losses in the circuit with a partial use of the flux produced by the coils and consequently with a low magnetic efficiency.
Another disadvantage to which current miniaturized relays are often subject is the difficulty in assembling the contact-holder block and the electromagnetic circuit-holder block and the adjustment thereof.
Not least, the need to insulate the contacts from the magnetic circuits by enlarging of surface distances in excess of 8 mm and a dielectric strength in excess of 4 KV, as required by the currently applicable norms, necessarily entails the use of insulating plates which sometimes cause an increase in the external dimensions of the relay with all the consequences which derive from this.